El state de Nevada requested that its new codigo de area be "lucky" 777; this fue denied por NANPA because it is an ERC, para be usados only para special purposes like inward Wide Area Telephone Service (Northern Nevada fue granted 775).]

a 3-numeros intercambio, indicating (amongst others) a Ciudad o other municipal area

a 4-numeros station numero

Traditionally, calling de one codigo de area para another, specifically para long distance calls, requires los caller para marcar los trunk numeros "1" before los codigos y numero. More recently, con los increasing numero y decreasing geografico size de Codigos de Area, it is possible para call a numero en another codigo de area that is not long distance, y such a call does require el codigo de area , but not los trunk numeros (initial "1").

Traditionally para avoid numero confusion, identical intercambio numeros en different Codigos de Area would be assigned as far apart de each other as possible, so that callers living near a state o NPA boundary would not get two areas en different NPAs confusados. Este made it possible en some low-density areas para use 7-numeros dialing even para reach areas en another codigo de area .[1 -

Before los advent de overlay plans, it fue universally accepted (and en some cases, required) that a call para a numero en los same codigo de area as los calling station be marcadoswithout including el codigo de area . As a result, los caller has para marcar only los 7 digitos de los intercambio plus los station numero.

It fue y also is possible para make a long distance call within los same codigo de area ; en this case los caller has para marcar a "1" before los local 7-digit numero. Until recently, en some cases, including el codigo de area when dialing such a numero would confGuia de telephone system, y prevent los call de being connected.

Este convention did not have a name until overlay plans introduced a requirement en some areas that all calls, even local, must be marcadospor including el codigo de area , i.e. 10-numeros dialing. Traditional 7-numeros dialing is still valid en those portions de los country not subject para an overlay plan.

In los Estados Unidos y Canada, - 10-numeros dialing - is a popular term usados para refer para los practice de including los area code de a telefono numero when dialing. Sometimes (see below), an initial "1" is usados; such dialing is known as 11-numeros dialing o national format.

"Standard" dialing

Traditionally, after los advent de Codigos de Area, los Telefono system allows callers para marcar only los local portion de los Numero de Telefono they wanted para reach, as long as los called numero fue en los same codigo de area as that de los caller. For example, a person whose full national Numero de Telefono is 212-555-7890 can call a numero located at 212-555-3456 por simply dialing 555-3456. El Telefono system infers that los desired numero fue en los same codigo de area , y connects los call accordingly. Este is now known retrospectively as 7-numeros dialing.

In this case, it is only necessary para marcar el codigo de area para a domestic call when el codigo de area de los called numero fue different de that de los calling numero. El Telefono system requires los caller para marcar a "1" before el codigo de area y numero, para indicate para los Telefono system that los call will require a connection para another area, as trunk Prefijo. ("1" is also los Codigo Telefonico Internacional para los North American numbering Plan including Estados Unidos y Canada, y therefore must likewise be marcadosbefore el codigo de area para internacional llamadas made para these countries.) Typically such llamadas were long distance calls. It usados para be a common misconception that a call para a different codigo de area fue por definition a long-distance call, but los significant growth en los numero de Codigos de Area (and los shrinking de los areas they occupy) since that time has invalidated this incorrect assumption.

In Canada y some regions de los United states, dialing a "1" before an codigo de area where los outgoing call is en los same service area results en an automated recording indicating that los call being made is local y a "1" is not necessary, even if los Codigos de Area son different. Este is common en areas where overlays son being usados. Telefono companies have also warned that dialing "1" when it is unnecessary could result en long distance charges being made even when they otherwise would not have been charged

Overlay plans

El introduction de overlay plans as a means para reduce los need para Numeros de Telefono para change as a result de adding new Codigos de Area meant that one geografico area could be associated con more than one codigo de area . Este is disadvantageous para new service providers as existing providers can issue numeros en los familiar codigo de area . en order para promote fairness among carriers, 10-numeros dialing became an FCC requirement; though los "1" before el codigo de area is often required only para actual long distance calls. Some Telefono systems en early overlay plan areas still do not accept a "1" before el codigo de area para non-long-distance calls.

As overlay plans have spread para more areas, 10-numeros dialing en los U.S. y Canada is becoming increasingly common. However, areas not within an overlay plan can still use 7-numeros dialing para local calls, although local long distance llamadas may require 10-numeros dialing even within los same codigo de area .

Originally, en North America, individual telephone intercambios were assigned entire individual Prefijoes, con all los 10,000 possible numeros (0000 para 9999) having that Prefijo being available (and only available) para that intercambio. ("Prefijo", "NXX", y "intercambio" son synonymous terms en NANP telephony.) Typically, one intercambio served one municipality (or rarely, groups de closely associated municipalities). As los growth de an area led para increased demands para Numeros de Telefono, more Prefijoes would be added.

Along con los advent de competition among telephone carriers, as well as Moviles telephone providers, each individual carrier serving a given municipality required its own Prefijoes. Este began para put pressure on los Prefijoes available within high-growth y high-competition areas, y led para a rapid increase en los introduction de new Codigos de Area.

9-1-1 y 4-1-1 work de nearly every telephone en los U.S. y Canada, while los others vary de place para place. Generally, only 4-1-1 llamadas incur a toll. 9-1-1 access is mandated por law, even on lines con no service (a "soft" dial tone). 6-1-1 (formerly 8-1-1) may also be accessible para activate service on such lines, y 3-1-1 may be available as well para urgent (but non-emergency) llamadas para police, o any call para local government en some places.

Other community servicios son provided through 2-1-1, but only if a non-profit organization such as los United Way operates it locally. Likewise, local o state/provincial government may o may not operate traffic information through 5-1-1. 8-1-1 fue made mandatory en los U.S. en 2007, as is 7-1-1. Unlike 9-1-1, these may o may not be available on a Telefono without paid service.